Ta. Dunn et al., COMPARATIVE CYTOTOXICITY OF OXALIPLATIN AND CISPLATIN IN NONSEMINOMATOUS GERM-CELL CANCER CELL-LINES, Investigational new drugs, 15(2), 1997, pp. 109-114
Approximately 70-80% of patients with metastatic testicular cancer wil
l become disease free with cisplatin-based chemotherapy and most of th
ese patients will be long-term survivors. Despite these impressive res
ults, the two limitations of cisplatin are its severe and potentially
long-term side-effects, and the emergence of drug resistance which pre
vents a small proportion of these patients from achieving long-term re
mission. Oxaliplatin has an improved toxicity profile compared to cisp
latin and contains the diaminocyclohexane (DACH) substituent known to
be correlated with a lack of cross-resistance with cisplatin. A phase
II study has shown interesting activity when used in combination with
cisplatin in cisplatin-refractory testicular cancer patients. Here we
report the results of the first in vitro study investigating whether o
xaliplatin as a single agent exhibits cross-resistance to cisplatin in
a panel of non-seminomatous germ cell tumor (NSGCT) cell lines using
short and long-term drug exposures in a five-day sulfhodamine B in vit
ro cytotoxicity assay. Oxaliplatin cytotoxicity was significantly supe
rior to cisplatin in cell lines with both acquired (H12DDP) and intrin
sic (1777NRp Cl-A) intermediate level resistance to cisplatin. Followi
ng 24h or 96h drug exposure the fold resistance in H12DDP and 1777NRp
Cl-A was 1.7-2.2 with oxaliplatin compared to 3.9-6.1 with cisplatin.
The cytotoxic activity of oxaliplatin was not significantly different
from that of cisplatin in cisplatin-senstive cell lines or in cell lin
es with a high level (10-20 fold) of cisplatin resistance. The results
of this study suggest that further preclinical studies in NSGCT are o
f interest, particularly in combination with cisplatin, ifosfamide and
etoposide. Furthermore, the in vitro results support the use of an ox
aliplatin administration schedule giving prolonged drug exposure, such
as the flat or circadian rhythm-modulated schedule already under inve
stigation for oxaliplatin.